In the design and specification of an antenna for any particular device, the antenna must often be adapted for use with the device. A properly adapted antenna allows the device to perform at its optimum level for given operating conditions.
One such type of “adaptation” is antenna matching or impedance matching, which is the process of adjusting the antenna's input impedance to be approximately equal to the characteristic impedance of the RF system over a specified range of frequencies. Assuming that the device is also designed or tuned to have an impedance approximately equal to the characteristic impedance, the antenna will be matched to the device.
Antenna matching is often achieved using a circuit containing one or more capacitors, resistors, inductors and possibly other lumped or pseudo-localized (transmission line, open or short circuit stub) components arranged in a network. These components and their characteristics are selected such that the output of the matching circuit when connected to the antenna has an impedance as seen from the device that is approximately equal to a desired impedance, e.g., the characteristic impedance.
A matching circuit is usually enclosed within the device, either as a separate element or as part of another circuit in the device. Before the design of the device is fixed, it is usually possible to accommodate the matching circuit. As devices that require antennas continue to decrease in size, however, internal space within the devices is very limited.
Most matching circuits are designed for a particular antenna and for a particular device. To use the antenna with a different device, or to use the device with a different antenna, a different matching circuit must be developed and substituted within the device. Making such a substitution may not be possible. Even if it possible, it may be difficult to access the existing matching circuit.
In the case of existing devices, there may be situations where an antenna needs to be added to a device that was designed without one. It may be necessary to replace an original antenna that is no longer available with a substitute model. Even if a replacement is available, it may exhibit slight differences in performance than the original. Any one of these factors, or a change in the device itself, may require that the antenna be re-adapted to the device.
One conventional type of antenna used in many applications is a whip antenna. A whip antenna has an elongated configuration, which may be rigid or resilient, and is attached at one end to the device. The attached end has a device interface for physically coupling the antenna and electrically connecting it to the device. Many conventional device interfaces are of the coaxial cable-type connection with a central wire or conductor surrounded by insulation, which in turn is surrounded by a grounded shield. Such conventional interfaces include SMA (Semi-Miniature A), stud, BNC (Bayonet Neil-Concelman) and many others.
It would be desirable to provide a methodology and structure for allowing flexible adaptation of antennas for use with different kinds of devices. It would be desirable to provide a solution for adapting a given antenna to a number of different devices without requiring changes to the dedicated circuitry enclosed within the device. It would also be desirable to provide a solution for reconfiguring certain conventional antennas to allow adaptation for different uses. It would also be desirable to provide a connector for applications other than antennas that is highly adaptable.